Code coverage metrics in Software Engineering - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is code coverage in software testing?

Code coverage is a measure that shows how much of the source code is tested by automated tests. It helps identify untested parts of a program.

beginner

Name the four common types of code coverage metrics.

The four common types are:
1. Line coverage
2. Branch coverage
3. Function coverage
4. Condition coverage

intermediate

What does branch coverage measure?

Branch coverage measures whether each possible branch (true or false) in decision points like if-else statements has been executed during testing.

intermediate

Why is 100% code coverage not always enough to guarantee bug-free software?

Because code coverage only shows which code was run, not whether the tests checked for correct behavior. Tests might run code without verifying results.

beginner

How can code coverage help improve software quality?

By showing which parts of code are not tested, developers can add tests to cover those areas, reducing the chance of hidden bugs.

Which code coverage type checks if every line of code has been executed?

A Function coverage

B Branch coverage

C Line coverage

D Condition coverage

Line coverage measures whether each line of code has been run during testing.

What does branch coverage focus on?

A Testing all functions

B Testing all decision paths

C Executing all lines

D Checking all variables

Branch coverage ensures all possible paths in decision points like if-else are tested.

If a test runs code but does not check if the output is correct, what does this imply about code coverage?

A Coverage is high but tests may be ineffective

B Coverage is low

C Tests are perfect

D Code is bug-free

Code coverage shows code was run, but without checking correctness, tests might miss bugs.

Which of these is NOT a common code coverage metric?

A Memory coverage

B Branch coverage

C Function coverage

D Line coverage

Memory coverage is not a standard code coverage metric.

How does code coverage help developers?

A By writing code for developers

B By fixing bugs automatically

C By running the software faster

D By showing untested code areas

Code coverage highlights which parts of code lack tests, guiding developers to improve testing.

Explain what code coverage metrics are and why they are useful in software testing.

Think about how testing shows which parts of code are checked.

Describe the difference between line coverage and branch coverage.

Consider simple code with if statements.

Practice

1. What does code coverage primarily measure in software testing?

easy

A. The number of developers working on the code

B. The number of bugs found in the code

C. The speed of the test execution

D. The percentage of code executed by tests

Solution

1. Step 1: Understand the purpose of code coverage

   Code coverage shows how much of the program's code is run during testing.

2. Step 2: Identify what code coverage measures

   It measures the percentage of code lines or branches executed by tests, not bugs or speed.

3. Final Answer:

   The percentage of code executed by tests -> Option D

4. Quick Check:

   Code coverage = executed code percentage [OK]

Hint: Code coverage = how much code tests run [OK]

Common Mistakes:

• Confusing coverage with bug count
• Thinking coverage measures test speed
• Assuming coverage counts developers

2. Which of the following is a common type of code coverage metric?

easy

A. Branch coverage

B. Memory coverage

C. Network coverage

D. User coverage

Solution

1. Step 1: Recall common code coverage types

   Common types include line coverage, branch coverage, and function coverage.

2. Step 2: Identify valid coverage types

   Branch coverage measures if all decision branches are tested; memory, network, and user coverage are not standard metrics.

3. Final Answer:

   Branch coverage -> Option A

4. Quick Check:

   Branch coverage is a standard metric [OK]

Hint: Branch coverage is a standard metric name [OK]

Common Mistakes:

• Choosing non-existent coverage types
• Confusing coverage with unrelated terms
• Ignoring common coverage categories

3. Consider a program with 100 lines of code. A test suite runs 80 lines and covers all branches in those lines. What is the approximate line coverage percentage?

medium

A. 20%

B. 100%

C. 80%

D. 50%

Solution

1. Step 1: Calculate line coverage

   Line coverage = (lines executed / total lines) x 100 = (80 / 100) x 100.

2. Step 2: Compute the percentage

   80 divided by 100 equals 0.8, multiplied by 100 gives 80% coverage.

3. Final Answer:

   80% -> Option C

4. Quick Check:

   80/100 = 0.8 = 80% [OK]

Hint: Divide executed lines by total lines, multiply by 100 [OK]

Common Mistakes:

• Confusing branch coverage with line coverage
• Calculating 100% because all branches covered
• Mixing up executed and total lines

4. A developer reports 90% code coverage, but some bugs remain. What is the most likely reason?

medium

A. High coverage does not guarantee all bugs are found

B. The coverage tool is broken

C. Tests ran too slowly

D. Code coverage measures bug count

Solution

1. Step 1: Understand code coverage limits

   Code coverage shows tested code amount but does not ensure test quality or bug detection.

2. Step 2: Identify why bugs remain

   Even with 90% coverage, tests might miss edge cases or logic errors causing bugs.

3. Final Answer:

   High coverage does not guarantee all bugs are found -> Option A

4. Quick Check:

   Coverage ≠ bug-free code [OK]

Hint: Coverage shows tested code, not bug absence [OK]

Common Mistakes:

• Assuming coverage means no bugs
• Blaming coverage tools without evidence
• Confusing coverage with test speed

5. You want to improve your test suite to cover all decision branches in a function with multiple if-else statements. Which approach best increases branch coverage?

hard

A. Write tests that only check the function's return value

B. Write tests that execute both true and false paths of each condition

C. Run the existing tests multiple times

D. Add print statements inside the function

Solution

1. Step 1: Understand branch coverage goal

   Branch coverage requires testing all possible paths of decision points (true and false).

2. Step 2: Choose the best testing approach

   Writing tests that cover both true and false branches ensures all decision paths run during testing.

3. Final Answer:

   Write tests that execute both true and false paths of each condition -> Option B

4. Quick Check:

   Branch coverage = test all decision paths [OK]

Hint: Test both true and false branches for full coverage [OK]

Common Mistakes:

• Testing only return values misses branches
• Rerunning tests doesn't increase coverage
• Adding print statements doesn't affect coverage